Minor changes to get negation working again.
Now can press "Enter" button on keyboard to draw graph.
Cursor changes to "loading" icon when drawing graph.
Minor bug fixes to parser to account for negative numbers in log and sqrt.
Help HTML page updated with new functions.
Updated the chart to use user-specified axes.
Threaded the SimpleParser implementation.
Threaded the Lexer
Added mathematical constants. Worked first try.
Added comment to constants class.
Added interface for formulae ready for switching implementations if we go native.
Fixed power function. Improved documentation.
Attempts to fix asymptotes. Needs proper testing.
Complete Java plugin system for functions and constants. Added standard library plugin project.
Merge branch 'jake/GUI' into jordan/plugins

Conflicts:
	MathsThing_GUI/src/uk/ac/uea/mathsthing/Functions.java
Fixed a problem that caused compiled versions of this to fail when loading plugins on Linux.
Added standard plugin libray to project. Added plugin security policy.
Fixed a problem with file paths on Windows and added plugin extensions for the GUI.
Created a better sample plugin for the extensions.
Fixed the PluginSystem throwing NullPointerException when no plugins were found.
Adds a rudy plugin for demoing of reading files in a plugin
Adds a security test plugin to show the security functionality blocking attempts at writing to files & closing the application.
Shows an error dialog when a plugin does something nasty when updating the formula
Minor changes to the product guide
Minor improvements to show formula plugin